HELIOX where to find information?

jaap · 22nd March 2006, 15:40

Quote: (Originally Posted by Mdemon)

Just a thought, but how appropriate would it be to use a trimix for descent on really deep dives, but immediately flush with heliox for the ascent?

The benefit being getting N2 out faster and keeping the helium lower (narcosis aside) - but would there be a problem in doing this? Is there a reaction to consider, along the lines of ICD but in reverse? I can't see what, but would be interested to hear from someone who's done it/knows about this...

So in your example the dive would be on a trimix but on leaving the target depth one would switch to heliox?

I think this could be dangerous from a potential isobaric counter diffusion (ICD) situation. I know a lot of people worry about ICD and that some just treat it as a theoretical thing that has no practical significans.

Anyway the theory would go that increasing the He fracion for the ascent increases the inspired He-partial pressure while decresing the inspired N2 pressure. This could lead to oversaturation in some compartments if He is going in faster than N2 is going out so that the total inert gas tension in some compartments increase to much possibly forming bubbles.

Mdemon · 22nd March 2006, 16:18

Quote: (Originally Posted by jaap)

So in your example the dive would be on a trimix but on leaving the target depth one would switch to heliox?

I think this could be dangerous from a potential isobaric counter diffusion (ICD) situation. I know a lot of people worry about ICD and that some just treat it as a theoretical thing that has no practical significans.

Anyway the theory would go that increasing the He fracion for the ascent increases the inspired He-partial pressure while decresing the inspired N2 pressure. This could lead to oversaturation in some compartments if He is going in faster than N2 is going out so that the total inert gas tension in some compartments increase to much possibly forming bubbles.

That's right - leave target depth and switch to heliox.

It was ICD I was curious about. My understanding was that when flushing with an N2-rich mix from a helium-rich/N2-light mix (as was common in the past), ICD was possible for the reasons you gave. However, we are talking about a situation in reverse - large molecules coming out and small molecules going in, albeit at a reduced rate (we're ascending and we've already been breathing He in the Mix).

I've already tried (without much success) to get my head round ICD so would be interested in views on this. My feeling is that ICD isn't an issue in this instance, but I'd like to hear other people's thoughts...

J. V. · 22nd March 2006, 16:28

Quote:

I've been trying to compare the deco obligations with trimix and Heliox.
Tx18/50 >Heliox 18/82
Can you say me wicth program do you use for calculate the deco?
With the programs that i've, the diference is "BRUTAL"

I use HSE computer in CF0, more liberal of three RGBM available, it's more or less like VPM-B nominal.
In VPM-B, 90 m for 20 min ppO2 1.3 give 109 min dive with tmx 10/70 and 124 min with Hx 10 ; 15 min difference.
With ZH-L 16 Bühlmann (in Nautilus) same Hx dive is 183 min...
I dive sometime with a buddy who have a VR3, he generally use tmx around 10/60 and me Hx 10, for a bounce dive around 100 meters difference of deco obligation is something like 20 to 30 min less for me (but I stay with him... if water is warm and if there is not big chocolate cake on the boat

)
These values are for one diluant for all the dive. By changing diluant during the ascent (Hx for Tmx), deco obligation can be seriously reduced, but I don't do it cause I belive to "keep it simple"

mverick · 22nd March 2006, 17:33

I just tried the HS Explorer simulator. Won't run RGBM for 10/90.

Kinda sucks...

ah well..

J. V. · 22nd March 2006, 18:03

Quote:

I just tried the HS Explorer simulator. Won't run RGBM for 10/90.

It don't perform RGBM at all, there is a commercial protection on RGBM algo.
By using "Dive Tables" key and "CF Comparison" you can see first stop, last stop and TTS for all algo, even RGBM.

mverick · 22nd March 2006, 18:18

Quote: (Originally Posted by J. V.)

It don't perform RGBM at all, there is a commercial protection on RGBM algo.
By using "Dive Tables" key and "CF Comparison" you can see first stop, last stop and TTS for all algo, even RGBM.

Thanks,

Haven't messed with it in a long, long, long time..

270ft for 20min on 10/90 1.3 ppo
CF0
tts 88min

CF3
tts 88min

CF9
tts 128

uri · 22nd March 2006, 18:25

Quote: (Originally Posted by Mdemon)

That's right - leave target depth and switch to heliox.

It was ICD I was curious about. My understanding was that when flushing with an N2-rich mix from a helium-rich/N2-light mix (as was common in the past), ICD was possible for the reasons you gave. However, we are talking about a situation in reverse - large molecules coming out and small molecules going in, albeit at a reduced rate (we're ascending and we've already been breathing He in the Mix).

I've already tried (without much success) to get my head round ICD so would be interested in views on this. My feeling is that ICD isn't an issue in this instance, but I'd like to hear other people's thoughts...

My understanding is that Nitrogen is large molecules and Helium small. So it's the reverse.

U

Mark Chase · 22nd March 2006, 23:30

Quote: (Originally Posted by uri)

My understanding is that Nitrogen is large molecules and Helium small. So it's the reverse.

U

Yes thats how i had it. Switching from He to Nitrogen is bad but from Nitrogen to He is good??

ATB

Mark Chase

jaap · 22nd March 2006, 23:55

Quote: (Originally Posted by Mdemon)

That's right - leave target depth and switch to heliox.

It was ICD I was curious about. My understanding was that when flushing with an N2-rich mix from a helium-rich/N2-light mix (as was common in the past), ICD was possible for the reasons you gave. However, we are talking about a situation in reverse - large molecules coming out and small molecules going in, albeit at a reduced rate (we're ascending and we've already been breathing He in the Mix).

I've already tried (without much success) to get my head round ICD so would be interested in views on this. My feeling is that ICD isn't an issue in this instance, but I'd like to hear other people's thoughts...

OK

Yes, maybe nothing bad will happen. I'm no expert but I think that slamming inert gas pressures by drastic changes in inspired gas, especially if done deep and after a deep dive makes for a potential ICD-problem.

As I know it the origin of ICD problems was from inspiring a "heavy" gas (low on He) while the body was exposed to a lighter gas (high on He). So that He would diffuse through the skin (This happend in some commercial diving situations and hyperbaric experiments). To me that effect does not sound to far from the case of a drastic switch to higher inspired He fraction at depth.

On the other hand if I understand the opinion of Dr Bruce Wienke (RGBM, isn't he also a CCR diver?) on this, going to a higher He-fraction is good and reducing it is bad while ascending. If I recall correctly from an OC deco discussion, his conclusion was that the best deco was from only increasing the O2 while reducing the N2 with the same fraction (thus holding the He-fraction rel constant).

Hard topic, lots of opinions, a few experimenters and no absolute answers...

Side note:
About a year ago I had an idea about using a second diluent with some Neon in it to reduce both N2 and He fractions at the same time for the ascent... Probably a bad idea since I didn't find anyone that had already tried it.
And I certainly wouldn't have any need to do that to myself...

Mdemon · 24th March 2006, 08:57

I don't think the changes would be that drastic, and actually I think changing to heliox at depth is possibly better, since you are further away from any ascent ceilings.

As the previous people have mentioned, I too think that going from He-light to He-rich mixes is OK; the reverse for N2 though. The only time I can see this being dodgy is at HPNS-risk depths. I suppose it could trigger an HPNS reaction. Admittedly, you would be ascending, and if on a high set point, the effects may be reduced. Perhaps DrJM might have an opinion on this?

(Some people have played with Neon. Rumour Control has it that one of the ladies at DDRC did dry tests to 200m on it... There are a few threads on here about using it. It looks like a great gas, but the downside is the expense.)

22nd March 2006, 15:40	#11 (permalink)
jaap Normal people worry me Current Rebreather/s: Classic Kiss Other CCR RB80 / Clone Ray Other SCR Home Build Other Rebreather/s: Other CCR RB80 / Clone Ray Other SCR Home Build Join Date: Jun 2005 Location: Stockholm Sweden Posts: 451	Re: HELIOX where to find information? Quote: (Originally Posted by Mdemon) Just a thought, but how appropriate would it be to use a trimix for descent on really deep dives, but immediately flush with heliox for the ascent? The benefit being getting N2 out faster and keeping the helium lower (narcosis aside) - but would there be a problem in doing this? Is there a reaction to consider, along the lines of ICD but in reverse? I can't see what, but would be interested to hear from someone who's done it/knows about this... So in your example the dive would be on a trimix but on leaving the target depth one would switch to heliox? I think this could be dangerous from a potential isobaric counter diffusion (ICD) situation. I know a lot of people worry about ICD and that some just treat it as a theoretical thing that has no practical significans. Anyway the theory would go that increasing the He fracion for the ascent increases the inspired He-partial pressure while decresing the inspired N2 pressure. This could lead to oversaturation in some compartments if He is going in faster than N2 is going out so that the total inert gas tension in some compartments increase to much possibly forming bubbles.
(Online)

22nd March 2006, 16:18	#12 (permalink)
Mdemon SiegeEngine II Current Rebreather/s: Inspiration Classic Home Build Other Rebreather/s: Inspiration Classic Home Build Join Date: Feb 2007 Location: SWUK Posts: 1,926	Re: HELIOX where to find information? Quote: (Originally Posted by jaap) So in your example the dive would be on a trimix but on leaving the target depth one would switch to heliox? I think this could be dangerous from a potential isobaric counter diffusion (ICD) situation. I know a lot of people worry about ICD and that some just treat it as a theoretical thing that has no practical significans. Anyway the theory would go that increasing the He fracion for the ascent increases the inspired He-partial pressure while decresing the inspired N2 pressure. This could lead to oversaturation in some compartments if He is going in faster than N2 is going out so that the total inert gas tension in some compartments increase to much possibly forming bubbles. That's right - leave target depth and switch to heliox. It was ICD I was curious about. My understanding was that when flushing with an N2-rich mix from a helium-rich/N2-light mix (as was common in the past), ICD was possible for the reasons you gave. However, we are talking about a situation in reverse - large molecules coming out and small molecules going in, albeit at a reduced rate (we're ascending and we've already been breathing He in the Mix). I've already tried (without much success) to get my head round ICD so would be interested in views on this. My feeling is that ICD isn't an issue in this instance, but I'd like to hear other people's thoughts... __________________ www.southwestmafia.com "small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!" The WRONG Attitude will get you killed. "Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"
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22nd March 2006, 16:28	#13 (permalink)
J. V. Custom Title Allowed! Current Rebreather/s: rEvo Other Rebreather/s: Not Bought Yet rEvo Join Date: Mar 2006 Location: Lot & Savoie Posts: 239	Re: HELIOX where to find information? Quote: I've been trying to compare the deco obligations with trimix and Heliox. Tx18/50 >Heliox 18/82 Can you say me wicth program do you use for calculate the deco? With the programs that i've, the diference is "BRUTAL" I use HSE computer in CF0, more liberal of three RGBM available, it's more or less like VPM-B nominal. In VPM-B, 90 m for 20 min ppO2 1.3 give 109 min dive with tmx 10/70 and 124 min with Hx 10 ; 15 min difference. With ZH-L 16 Bühlmann (in Nautilus) same Hx dive is 183 min... I dive sometime with a buddy who have a VR3, he generally use tmx around 10/60 and me Hx 10, for a bounce dive around 100 meters difference of deco obligation is something like 20 to 30 min less for me (but I stay with him... if water is warm and if there is not big chocolate cake on the boat ) These values are for one diluant for all the dive. By changing diluant during the ascent (Hx for Tmx), deco obligation can be seriously reduced, but I don't do it cause I belive to "keep it simple" __________________ -------------------- Jacques NPSFQQA-EDS IT # 007 (remué non agité)
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22nd March 2006, 17:33	#14 (permalink)
mverick ScubaPimp Current Rebreather/s: Megalodon Other CCR Home Build Other Rebreather/s: Other CCR Home Build Join Date: Aug 2005 Posts: 542	Re: HELIOX where to find information? I just tried the HS Explorer simulator. Won't run RGBM for 10/90. Kinda sucks... ah well..
(Online)

22nd March 2006, 18:03	#15 (permalink)
J. V. Custom Title Allowed! Current Rebreather/s: rEvo Other Rebreather/s: Not Bought Yet rEvo Join Date: Mar 2006 Location: Lot & Savoie Posts: 239	Re: HELIOX where to find information? Quote: I just tried the HS Explorer simulator. Won't run RGBM for 10/90. It don't perform RGBM at all, there is a commercial protection on RGBM algo. By using "Dive Tables" key and "CF Comparison" you can see first stop, last stop and TTS for all algo, even RGBM. __________________ -------------------- Jacques NPSFQQA-EDS IT # 007 (remué non agité)
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22nd March 2006, 18:18	#16 (permalink)
mverick ScubaPimp Current Rebreather/s: Megalodon Other CCR Home Build Other Rebreather/s: Other CCR Home Build Join Date: Aug 2005 Posts: 542	Re: HELIOX where to find information? Quote: (Originally Posted by J. V.) It don't perform RGBM at all, there is a commercial protection on RGBM algo. By using "Dive Tables" key and "CF Comparison" you can see first stop, last stop and TTS for all algo, even RGBM. Thanks, Haven't messed with it in a long, long, long time.. 270ft for 20min on 10/90 1.3 ppo CF0 tts 88min CF3 tts 88min CF9 tts 128
(Online)

22nd March 2006, 18:25	#17 (permalink)
uri Uri Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Apr 2005 Location: Sandhurst UK Posts: 37	Re: HELIOX where to find information? Quote: (Originally Posted by Mdemon) That's right - leave target depth and switch to heliox. It was ICD I was curious about. My understanding was that when flushing with an N2-rich mix from a helium-rich/N2-light mix (as was common in the past), ICD was possible for the reasons you gave. However, we are talking about a situation in reverse - large molecules coming out and small molecules going in, albeit at a reduced rate (we're ascending and we've already been breathing He in the Mix). I've already tried (without much success) to get my head round ICD so would be interested in views on this. My feeling is that ICD isn't an issue in this instance, but I'd like to hear other people's thoughts... My understanding is that Nitrogen is large molecules and Helium small. So it's the reverse. U
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22nd March 2006, 23:30	#18 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,699	Re: HELIOX where to find information? Quote: (Originally Posted by uri) My understanding is that Nitrogen is large molecules and Helium small. So it's the reverse. U Yes thats how i had it. Switching from He to Nitrogen is bad but from Nitrogen to He is good?? ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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22nd March 2006, 23:55	#19 (permalink)
jaap Normal people worry me Current Rebreather/s: Classic Kiss Other CCR RB80 / Clone Ray Other SCR Home Build Other Rebreather/s: Other CCR RB80 / Clone Ray Other SCR Home Build Join Date: Jun 2005 Location: Stockholm Sweden Posts: 451	Re: HELIOX where to find information? Quote: (Originally Posted by Mdemon) That's right - leave target depth and switch to heliox. It was ICD I was curious about. My understanding was that when flushing with an N2-rich mix from a helium-rich/N2-light mix (as was common in the past), ICD was possible for the reasons you gave. However, we are talking about a situation in reverse - large molecules coming out and small molecules going in, albeit at a reduced rate (we're ascending and we've already been breathing He in the Mix). I've already tried (without much success) to get my head round ICD so would be interested in views on this. My feeling is that ICD isn't an issue in this instance, but I'd like to hear other people's thoughts... OK Yes, maybe nothing bad will happen. I'm no expert but I think that slamming inert gas pressures by drastic changes in inspired gas, especially if done deep and after a deep dive makes for a potential ICD-problem. As I know it the origin of ICD problems was from inspiring a "heavy" gas (low on He) while the body was exposed to a lighter gas (high on He). So that He would diffuse through the skin (This happend in some commercial diving situations and hyperbaric experiments). To me that effect does not sound to far from the case of a drastic switch to higher inspired He fraction at depth. On the other hand if I understand the opinion of Dr Bruce Wienke (RGBM, isn't he also a CCR diver?) on this, going to a higher He-fraction is good and reducing it is bad while ascending. If I recall correctly from an OC deco discussion, his conclusion was that the best deco was from only increasing the O2 while reducing the N2 with the same fraction (thus holding the He-fraction rel constant). Hard topic, lots of opinions, a few experimenters and no absolute answers... Side note: About a year ago I had an idea about using a second diluent with some Neon in it to reduce both N2 and He fractions at the same time for the ascent... Probably a bad idea since I didn't find anyone that had already tried it. And I certainly wouldn't have any need to do that to myself...
(Online)

24th March 2006, 08:57	#20 (permalink)
Mdemon SiegeEngine II Current Rebreather/s: Inspiration Classic Home Build Other Rebreather/s: Inspiration Classic Home Build Join Date: Feb 2007 Location: SWUK Posts: 1,926	Re: HELIOX where to find information? I don't think the changes would be that drastic, and actually I think changing to heliox at depth is possibly better, since you are further away from any ascent ceilings. As the previous people have mentioned, I too think that going from He-light to He-rich mixes is OK; the reverse for N2 though. The only time I can see this being dodgy is at HPNS-risk depths. I suppose it could trigger an HPNS reaction. Admittedly, you would be ascending, and if on a high set point, the effects may be reduced. Perhaps DrJM might have an opinion on this? (Some people have played with Neon. Rumour Control has it that one of the ladies at DDRC did dry tests to 200m on it... There are a few threads on here about using it. It looks like a great gas, but the downside is the expense.) __________________ www.southwestmafia.com "small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!" The WRONG Attitude will get you killed. "Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"
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